<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
    <script>
    let data=new FormData();

    data.set('user', 'blue');
    data.append('user', 'blue2');

    console.log(data.getAll('user'));
    </script>
  </head>
  <body>

  </body>
</html>
